Increase of tuberculous infection in the organs of B cell-deficient mice

Protective immunity against infection with Mycobacterium tuberculosis is imparted by T cells rather than antibodies, but B cells can play a role as antigen-presenting cells and in granuloma formation. We re-evaluated the role of B cells in the course of tuberculous infection in μ-chain knock-out (Ig⁻) mice. Surprisingly, the organs of M. tuberculosis-infected Ig⁻ mice were found to have three-to eight-fold elevated counts of viable bacilli compared with normal littermates at 3–6 weeks post-infection. Splenic interferon-gamma responses to whole antigen were unimpaired, whilst proliferation to certain mycobacterial peptides was found to be diminished. However, bacille Calmette–Guérin (BCG) vaccination significantly reduced the infection in Ig⁻ mice. The mechanisms by which B cells can influence primary tuberculous infection need further study.